Attic sealing with existing loose fill insulation – practical advice
Hey all, I previously posted about my new old 1943 house in East TN (1200 sqft original with a 350 sqft vaulted addition, crawl space, in Climate Zone 4). I recently closed on the house and am assessing how I’m going to address the “invisible” issues – this week I’m obsessing about the attic (vented and unfinished). I have very little contruction experience but am learning as I go, and my thermo knowledge is pretty strong.
The house has a vented attic (ridge vent, soffit vents, and gable vents) and has some combination of faced cellulose batts and loose fill as well as faced fiberglass batts in the attic. Appears to be a collection of legacy (batts) and new (loose fill) efforts. Combined insulation highest point is maybe 2′, but average height is closer to 1′. Miscellaneous decking for storage/walking has been installed around the attic entrance with batts underneath. HVAC is a 10-year old Trane unit (no natural gas heating, will upgrade to gas pack when it bites the dust) and a wood stove backfitted into the original masonry fireplace.
I understand that air sealing is very important from reading several GBA articles, especially at the ceiling/attic interface. The extent of air sealing (e.g. around the masonry fireplace, top plates of walls, electrical holes in top plates) is unknown, but I’m assuming the worst. I haven’t dug past the insulation yet to verify but I will. Let’s just say the ceiling attic door is totally without weatherstripping or insulation so it’s rather unlikely that the homeowner or any contractor performed methodical air sealing at the ceiling/attic interface.
So when I dig past the batts and see that nothing has been sealed, I plan on doing it myself. My eventual game plan after sealing would be to attain a high R value with additional or new loose fill cellulose (don’t plan on attic storage). I have a few practical questions I was curious if anyone could help me with:
1. A few Youtubers have opted to remove ALL existing loose fill from their attic using vacuum rigs, e.g. https://www.youtube.com/watch?v=CasxSXYR3m4 and https://www.youtube.com/watch?v=xXjo-KCAPbA . Another option I can think of working on one zone at a time after moving the loose fill (say with a snow shovel and/or rake into trash bags) and batts in that zone aside, then replacing the insulation after finishing sealing each zone. I’m sort of worried that I might be overly optimistic on my zone approach and was curious what other folks might think?
I guess I could give it a shot first. The loose fill vacuum removal approach would cost more and require additional logistics (outdoor “insulation catch” for instance) but if it’s best for some reason I’m not considering now then I could be persueded to go that route. For instance, I know that fiberglass loose fill compacts over time, so some people might just want to ditch it entirely, but it seems more reasonable to just blow in additional cellulose fill on top.
2. I’m having a tough time finding well-reasoned recommendations for caulk and/or expanding foam products for attic applications. Does anyone have any experience here?
3. It’s pretty warm right now but will begin getting into sub-freezing weather soon. I’m curious if the foam/caulk I use will run into curing issues as a result of the temperature – any comments here? Obviously I would also check the spec sheets of the products I choose.
4. Any other considerations to think about? I plan on wearing a P100 respirator, putting down OSB/plywood sheets across the ceiling joists to stand/sit on, etc.
Thank you very much!
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